Effects of hysteresis energy and mean stress on low-cycle fatigue behaviors of an extruded magnesium alloy

Extruded Mg–3% Al–1% Zn alloy (AZ31) plate often exhibits quite different strength and plasticity along two directions (extruded direction, ED; transverse direction, TD) under tension and compression conditions. In particular, the hysteresis loops of ED and TD samples display obviously different shapes in the total strain amplitude range from 0.1% to 1%. Accordingly, the low-cycle fatigue lives of TD samples are found to be longer than those of ED samples, which can be attributed to the difference in the mean stress and hysteresis energy.

► The tensile yield strength of the AZ31 plate along extruded direction (ED) is higher than transverse direction (TD), but elongation of ED sample is about half of TD samples.
► The hysteresis loops for ED samples shows S-shape and quite asymmetry at a series of total strain amplitudes, while the hysteresis loops of TD samples are quite symmetric.
► The low-cycle fatigue lives of TD samples are always longer than those of ED samples at the same total strain amplitude.